Fiberglass, rockwool and cellulose-based materials are commonly used as building insulation. All have the benefit of having very good insulation performance (high so-called “R-values”). Fiberglass and rockwool are often installed in the form of batting which is stapled in wall cavities (such as between supporting members) in a structure. However, fiberglass, rockwool and cellulose based materials can be placed in such cavities by being blown into place as loose fill. When installed in this fashion, the material tends to conform to and more completely fill the cavity. That is, fiberglass batting does not conform as closely to framing, piping, wiring and other in-wall obstructions as does blown insulation. Thus, blown materials more completely fill the cavity and better limit air infiltration into and through the cavities in which they are placed.
It is known that blown cellulose insulation (typically made from recycled paper treated with fire-retardant chemicals such as boric acid and ammonia sulfate) can be even more effectively placed through a combination of pneumatic blowing and hydraulic spraying. In such methods, the insulation is pneumatically blown into a wall cavity through a two and one-half inch or larger diameter flexible hose connected to an insulation-blowing machine. The hose outlet is fitted with spray tips that are in-turn connected to a high-pressure water source (e.g. 150 p.s.i.). As the insulation is blown into a cavity it is mixed with the spray water. As water is absorbed into or becomes attached to the surface of the material it becomes heavier and stickier which allows the material to pack and more completely fill the wall cavity. Since the insulating material is more densely packed thoroughly filling the cavity, the insulation performance is improved over installations in which only dry material is blown into place.
There are drawbacks to using wetted insulation materials. In order to avoid possible microbial growth it is appropriate to dry the wetted insulation. Drying occurs much faster when the insulation in the cavity remains exposed, so all or some drying is done before proceeding with closure of the insulated cavity. The time necessary for this drying step depends on the amount of water used in the process, ambient humidity, the thickness of the material deposited in the wall, and fresh air flow after the process. Typically the insulation as deposited will range from 30-60% moisture. It is desirable to dry the material to no more than about 18% moisture before closing the wall.
Closing the wall before the insulation is adequately dried increases the risk of mold growth on the insulation, the framing members, gypsum board and the interior walls. This is particularly the case with insulation materials that include fire retardants that may actually promote mold growth (ammonia sulfate). However, the need to move quickly during a construction project makes it difficult to wait the 24-60 hours that can be required to permit the insulation to dry adequately before closing the wall or other cavity. This practical consideration has limited the use of wetted insulation materials, despite their long-term beneficial impacts on energy savings.